Odd Occurence in Black Temple

So tonight while doing my weekly Black Temple run for the warglaives, i noticed something i hadnt notice before. When Illidan hit about 10-15%, Maeiv placed some sort of mechanical engineering box- like thing on the ground. Just out of curiosity i drug Illidan over to it before he died and when he did, it made blue energy fields around his dying body, then proceeded to close. And Illidan's corpse laid on the ground like normal.

Was wondering if this is something that happens every run and i just dont pay attention, or maybe something they added in 5.1. Real curious though with all the return of Illidan hype. Hope someone can confirm that theyve seen this as well!

Yeah it always happened. Back in the day, tanks had to kite him over those traps. Don't remember what they did though

It stunned him, preventing him from enraging, and he took increased damage, both for the remainder of the phase. Depending on tank and placement, ~10 seconds of increased damage before he used metamorphosis.

It was used to dispell the enrage effect on Illidan during the last phase and as a bonus made him take more damage while he was trapped.

As a DK everything there is a faceroll. Council takes a while but I just focused the healer and stood in the aoe as I took hardly any damage. Got my oh glaive on my first solo run :P got right binding too! jammy little git.